Digallane

Digallane, Ga₂H₆, is prepared by below reaction; the product condenses at low temperature as a white solid (mp 223 K) but decomposes above 253 K.

Figure 1.1 summarizes some reactions of B₂H₆ and Ga₂H₆. Compared with the much studied B₂H₆, Ga₂H₆ has received only recent attention, and not all reaction types can be compared. However, three points should be noted:

•  Ga₂H₆ is unlike B₂H₆ in that Ga₂H₆ rapidly decomposes to its constituent elements;
• Ga₂H₆ and B₂H₆ both react with HCl, but in the case of the borane, substitution of a terminal

• Ga₂H₆ is like B₂H₆ in that it reacts with Lewis bases.

   This last class of reaction is well documented and the examples in Figure 1.1 illustrate two reaction types with the steric demands of the Lewis base being an important factor in determining which pathway predominates. For example, two NH₃ molecules can attack the same B or Ga centre, resulting in asymmetric cleavage of the E₂H₆ molecule; in contrast, reactions with more sterically demanding Lewis bases tend to cause symmetric cleavage.